// SPDX-License-Identifier: GPL-2.0 /* * INET An implementation of the TCP/IP protocol suite for the LINUX * operating system. INET is implemented using the BSD Socket * interface as the means of communication with the user level. * * The IP fragmentation functionality. * * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG> * Alan Cox <alan@lxorguk.ukuu.org.uk> * * Fixes: * Alan Cox : Split from ip.c , see ip_input.c for history. * David S. Miller : Begin massive cleanup... * Andi Kleen : Add sysctls. * xxxx : Overlapfrag bug. * Ultima : ip_expire() kernel panic. * Bill Hawes : Frag accounting and evictor fixes. * John McDonald : 0 length frag bug. * Alexey Kuznetsov: SMP races, threading, cleanup. * Patrick McHardy : LRU queue of frag heads for evictor. */ #define pr_fmt(fmt) "IPv4: " fmt #include <linux/compiler.h> #include <linux/module.h> #include <linux/types.h> #include <linux/mm.h> #include <linux/jiffies.h> #include <linux/skbuff.h> #include <linux/list.h> #include <linux/ip.h> #include <linux/icmp.h> #include <linux/netdevice.h> #include <linux/jhash.h> #include <linux/random.h> #include <linux/slab.h> #include <net/route.h> #include <net/dst.h> #include <net/sock.h> #include <net/ip.h> #include <net/icmp.h> #include <net/checksum.h> #include <net/inetpeer.h> #include <net/inet_frag.h> #include <linux/tcp.h> #include <linux/udp.h> #include <linux/inet.h> #include <linux/netfilter_ipv4.h> #include <net/inet_ecn.h> #include <net/l3mdev.h> /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c * as well. Or notify me, at least. --ANK */ static const char ip_frag_cache_name[] = "ip4-frags"; /* Describe an entry in the "incomplete datagrams" queue. */ struct ipq { struct inet_frag_queue q; u8 ecn; /* RFC3168 support */ u16 max_df_size; /* largest frag with DF set seen */ int iif; unsigned int rid; struct inet_peer *peer; }; static u8 ip4_frag_ecn(u8 tos) { return 1 << (tos & INET_ECN_MASK); } static struct inet_frags ip4_frags; static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb, struct sk_buff *prev_tail, struct net_device *dev); static void ip4_frag_init(struct inet_frag_queue *q, const void *a) { struct ipq *qp = container_of(q, struct ipq, q); struct net *net = q->fqdir->net; const struct frag_v4_compare_key *key = a; q->key.v4 = *key; qp->ecn = 0; qp->peer = q->fqdir->max_dist ? inet_getpeer_v4(net->ipv4.peers, key->saddr, key->vif, 1) : NULL; } static void ip4_frag_free(struct inet_frag_queue *q) { struct ipq *qp; qp = container_of(q, struct ipq, q); if (qp->peer) inet_putpeer(qp->peer); } /* Destruction primitives. */ static void ipq_put(struct ipq *ipq) { inet_frag_put(&ipq->q); } /* Kill ipq entry. It is not destroyed immediately, * because caller (and someone more) holds reference count. */ static void ipq_kill(struct ipq *ipq) { inet_frag_kill(&ipq->q); } static bool frag_expire_skip_icmp(u32 user) { return user == IP_DEFRAG_AF_PACKET || ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN, __IP_DEFRAG_CONNTRACK_IN_END) || ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN, __IP_DEFRAG_CONNTRACK_BRIDGE_IN); } /* * Oops, a fragment queue timed out. Kill it and send an ICMP reply. */ static void ip_expire(struct timer_list *t) { struct inet_frag_queue *frag = from_timer(frag, t, timer); const struct iphdr *iph; struct sk_buff *head = NULL; struct net *net; struct ipq *qp; int err; qp = container_of(frag, struct ipq, q); net = qp->q.fqdir->net; rcu_read_lock(); if (qp->q.fqdir->dead) goto out_rcu_unlock; spin_lock(&qp->q.lock); if (qp->q.flags & INET_FRAG_COMPLETE) goto out; ipq_kill(qp); __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); __IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT); if (!(qp->q.flags & INET_FRAG_FIRST_IN)) goto out; /* sk_buff::dev and sk_buff::rbnode are unionized. So we * pull the head out of the tree in order to be able to * deal with head->dev. */ head = inet_frag_pull_head(&qp->q); if (!head) goto out; head->dev = dev_get_by_index_rcu(net, qp->iif); if (!head->dev) goto out; /* skb has no dst, perform route lookup again */ iph = ip_hdr(head); err = ip_route_input_noref(head, iph->daddr, iph->saddr, iph->tos, head->dev); if (err) goto out; /* Only an end host needs to send an ICMP * "Fragment Reassembly Timeout" message, per RFC792. */ if (frag_expire_skip_icmp(qp->q.key.v4.user) && (skb_rtable(head)->rt_type != RTN_LOCAL)) goto out; spin_unlock(&qp->q.lock); icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0); goto out_rcu_unlock; out: spin_unlock(&qp->q.lock); out_rcu_unlock: rcu_read_unlock(); kfree_skb(head); ipq_put(qp); } /* Find the correct entry in the "incomplete datagrams" queue for * this IP datagram, and create new one, if nothing is found. */ static struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user, int vif) { struct frag_v4_compare_key key = { .saddr = iph->saddr, .daddr = iph->daddr, .user = user, .vif = vif, .id = iph->id, .protocol = iph->protocol, }; struct inet_frag_queue *q; q = inet_frag_find(net->ipv4.fqdir, &key); if (!q) return NULL; return container_of(q, struct ipq, q); } /* Is the fragment too far ahead to be part of ipq? */ static int ip_frag_too_far(struct ipq *qp) { struct inet_peer *peer = qp->peer; unsigned int max = qp->q.fqdir->max_dist; unsigned int start, end; int rc; if (!peer || !max) return 0; start = qp->rid; end = atomic_inc_return(&peer->rid); qp->rid = end; rc = qp->q.fragments_tail && (end - start) > max; if (rc) __IP_INC_STATS(qp->q.fqdir->net, IPSTATS_MIB_REASMFAILS); return rc; } static int ip_frag_reinit(struct ipq *qp) { unsigned int sum_truesize = 0; if (!mod_timer(&qp->q.timer, jiffies + qp->q.fqdir->timeout)) { refcount_inc(&qp->q.refcnt); return -ETIMEDOUT; } sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments); sub_frag_mem_limit(qp->q.fqdir, sum_truesize); qp->q.flags = 0; qp->q.len = 0; qp->q.meat = 0; qp->q.rb_fragments = RB_ROOT; qp->q.fragments_tail = NULL; qp->q.last_run_head = NULL; qp->iif = 0; qp->ecn = 0; return 0; } /* Add new segment to existing queue. */ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) { struct net *net = qp->q.fqdir->net; int ihl, end, flags, offset; struct sk_buff *prev_tail; struct net_device *dev; unsigned int fragsize; int err = -ENOENT; u8 ecn; if (qp->q.flags & INET_FRAG_COMPLETE) goto err; if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) && unlikely(ip_frag_too_far(qp)) && unlikely(err = ip_frag_reinit(qp))) { ipq_kill(qp); goto err; } ecn = ip4_frag_ecn(ip_hdr(skb)->tos); offset = ntohs(ip_hdr(skb)->frag_off); flags = offset & ~IP_OFFSET; offset &= IP_OFFSET; offset <<= 3; /* offset is in 8-byte chunks */ ihl = ip_hdrlen(skb); /* Determine the position of this fragment. */ end = offset + skb->len - skb_network_offset(skb) - ihl; err = -EINVAL; /* Is this the final fragment? */ if ((flags & IP_MF) == 0) { /* If we already have some bits beyond end * or have different end, the segment is corrupted. */ if (end < qp->q.len || ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len)) goto discard_qp; qp->q.flags |= INET_FRAG_LAST_IN; qp->q.len = end; } else { if (end&7) { end &= ~7; if (skb->ip_summed != CHECKSUM_UNNECESSARY) skb->ip_summed = CHECKSUM_NONE; } if (end > qp->q.len) { /* Some bits beyond end -> corruption. */ if (qp->q.flags & INET_FRAG_LAST_IN) goto discard_qp; qp->q.len = end; } } if (end == offset) goto discard_qp; err = -ENOMEM; if (!pskb_pull(skb, skb_network_offset(skb) + ihl)) goto discard_qp; err = pskb_trim_rcsum(skb, end - offset); if (err) goto discard_qp; /* Note : skb->rbnode and skb->dev share the same location. */ dev = skb->dev; /* Makes sure compiler wont do silly aliasing games */ barrier(); prev_tail = qp->q.fragments_tail; err = inet_frag_queue_insert(&qp->q, skb, offset, end); if (err) goto insert_error; if (dev) qp->iif = dev->ifindex; qp->q.stamp = skb->tstamp; qp->q.meat += skb->len; qp->ecn |= ecn; add_frag_mem_limit(qp->q.fqdir, skb->truesize); if (offset == 0) qp->q.flags |= INET_FRAG_FIRST_IN; fragsize = skb->len + ihl; if (fragsize > qp->q.max_size) qp->q.max_size = fragsize; if (ip_hdr(skb)->frag_off & htons(IP_DF) && fragsize > qp->max_df_size) qp->max_df_size = fragsize; if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) && qp->q.meat == qp->q.len) { unsigned long orefdst = skb->_skb_refdst; skb->_skb_refdst = 0UL; err = ip_frag_reasm(qp, skb, prev_tail, dev); skb->_skb_refdst = orefdst; if (err) inet_frag_kill(&qp->q); return err; } skb_dst_drop(skb); return -EINPROGRESS; insert_error: if (err == IPFRAG_DUP) { kfree_skb(skb); return -EINVAL; } err = -EINVAL; __IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS); discard_qp: inet_frag_kill(&qp->q); __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); err: kfree_skb(skb); return err; } static bool ip_frag_coalesce_ok(const struct ipq *qp) { return qp->q.key.v4.user == IP_DEFRAG_LOCAL_DELIVER; } /* Build a new IP datagram from all its fragments. */ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb, struct sk_buff *prev_tail, struct net_device *dev) { struct net *net = qp->q.fqdir->net; struct iphdr *iph; void *reasm_data; int len, err; u8 ecn; ipq_kill(qp); ecn = ip_frag_ecn_table[qp->ecn]; if (unlikely(ecn == 0xff)) { err = -EINVAL; goto out_fail; } /* Make the one we just received the head. */ reasm_data = inet_frag_reasm_prepare(&qp->q, skb, prev_tail); if (!reasm_data) goto out_nomem; len = ip_hdrlen(skb) + qp->q.len; err = -E2BIG; if (len > 65535) goto out_oversize; inet_frag_reasm_finish(&qp->q, skb, reasm_data, ip_frag_coalesce_ok(qp)); skb->dev = dev; IPCB(skb)->frag_max_size = max(qp->max_df_size, qp->q.max_size); iph = ip_hdr(skb); iph->tot_len = htons(len); iph->tos |= ecn; /* When we set IP_DF on a refragmented skb we must also force a * call to ip_fragment to avoid forwarding a DF-skb of size s while * original sender only sent fragments of size f (where f < s). * * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest * frag seen to avoid sending tiny DF-fragments in case skb was built * from one very small df-fragment and one large non-df frag. */ if (qp->max_df_size == qp->q.max_size) { IPCB(skb)->flags |= IPSKB_FRAG_PMTU; iph->frag_off = htons(IP_DF); } else { iph->frag_off = 0; } ip_send_check(iph); __IP_INC_STATS(net, IPSTATS_MIB_REASMOKS); qp->q.rb_fragments = RB_ROOT; qp->q.fragments_tail = NULL; qp->q.last_run_head = NULL; return 0; out_nomem: net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp); err = -ENOMEM; goto out_fail; out_oversize: net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->q.key.v4.saddr); out_fail: __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); return err; } /* Process an incoming IP datagram fragment. */ int ip_defrag(struct net *net, struct sk_buff *skb, u32 user) { struct net_device *dev = skb->dev ? : skb_dst(skb)->dev; int vif = l3mdev_master_ifindex_rcu(dev); struct ipq *qp; __IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS); skb_orphan(skb); /* Lookup (or create) queue header */ qp = ip_find(net, ip_hdr(skb), user, vif); if (qp) { int ret; spin_lock(&qp->q.lock); ret = ip_frag_queue(qp, skb); spin_unlock(&qp->q.lock); ipq_put(qp); return ret; } __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS); kfree_skb(skb); return -ENOMEM; } EXPORT_SYMBOL(ip_defrag); struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user) { struct iphdr iph; int netoff; u32 len; if (skb->protocol != htons(ETH_P_IP)) return skb; netoff = skb_network_offset(skb); if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0) return skb; if (iph.ihl < 5 || iph.version != 4) return skb; len = ntohs(iph.tot_len); if (skb->len < netoff + len || len < (iph.ihl * 4)) return skb; if (ip_is_fragment(&iph)) { skb = skb_share_check(skb, GFP_ATOMIC); if (skb) { if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) { kfree_skb(skb); return NULL; } if (pskb_trim_rcsum(skb, netoff + len)) { kfree_skb(skb); return NULL; } memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); if (ip_defrag(net, skb, user)) return NULL; skb_clear_hash(skb); } } return skb; } EXPORT_SYMBOL(ip_check_defrag); #ifdef CONFIG_SYSCTL static int dist_min; static struct ctl_table ip4_frags_ns_ctl_table[] = { { .procname = "ipfrag_high_thresh", .maxlen = sizeof(unsigned long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, }, { .procname = "ipfrag_low_thresh", .maxlen = sizeof(unsigned long), .mode = 0644, .proc_handler = proc_doulongvec_minmax, }, { .procname = "ipfrag_time", .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { .procname = "ipfrag_max_dist", .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = &dist_min, }, { } }; /* secret interval has been deprecated */ static int ip4_frags_secret_interval_unused; static struct ctl_table ip4_frags_ctl_table[] = { { .procname = "ipfrag_secret_interval", .data = &ip4_frags_secret_interval_unused, .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec_jiffies, }, { } }; static int __net_init ip4_frags_ns_ctl_register(struct net *net) { struct ctl_table *table; struct ctl_table_header *hdr; table = ip4_frags_ns_ctl_table; if (!net_eq(net, &init_net)) { table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL); if (!table) goto err_alloc; } table[0].data = &net->ipv4.fqdir->high_thresh; table[0].extra1 = &net->ipv4.fqdir->low_thresh; table[1].data = &net->ipv4.fqdir->low_thresh; table[1].extra2 = &net->ipv4.fqdir->high_thresh; table[2].data = &net->ipv4.fqdir->timeout; table[3].data = &net->ipv4.fqdir->max_dist; hdr = register_net_sysctl(net, "net/ipv4", table); if (!hdr) goto err_reg; net->ipv4.frags_hdr = hdr; return 0; err_reg: if (!net_eq(net, &init_net)) kfree(table); err_alloc: return -ENOMEM; } static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net) { struct ctl_table *table; table = net->ipv4.frags_hdr->ctl_table_arg; unregister_net_sysctl_table(net->ipv4.frags_hdr); kfree(table); } static void __init ip4_frags_ctl_register(void) { register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table); } #else static int ip4_frags_ns_ctl_register(struct net *net) { return 0; } static void ip4_frags_ns_ctl_unregister(struct net *net) { } static void __init ip4_frags_ctl_register(void) { } #endif static int __net_init ipv4_frags_init_net(struct net *net) { int res; res = fqdir_init(&net->ipv4.fqdir, &ip4_frags, net); if (res < 0) return res; /* Fragment cache limits. * * The fragment memory accounting code, (tries to) account for * the real memory usage, by measuring both the size of frag * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue)) * and the SKB's truesize. * * A 64K fragment consumes 129736 bytes (44*2944)+200 * (1500 truesize == 2944, sizeof(struct ipq) == 200) * * We will commit 4MB at one time. Should we cross that limit * we will prune down to 3MB, making room for approx 8 big 64K * fragments 8x128k. */ net->ipv4.fqdir->high_thresh = 4 * 1024 * 1024; net->ipv4.fqdir->low_thresh = 3 * 1024 * 1024; /* * Important NOTE! Fragment queue must be destroyed before MSL expires. * RFC791 is wrong proposing to prolongate timer each fragment arrival * by TTL. */ net->ipv4.fqdir->timeout = IP_FRAG_TIME; net->ipv4.fqdir->max_dist = 64; res = ip4_frags_ns_ctl_register(net); if (res < 0) fqdir_exit(net->ipv4.fqdir); return res; } static void __net_exit ipv4_frags_pre_exit_net(struct net *net) { fqdir_pre_exit(net->ipv4.fqdir); } static void __net_exit ipv4_frags_exit_net(struct net *net) { ip4_frags_ns_ctl_unregister(net); fqdir_exit(net->ipv4.fqdir); } static struct pernet_operations ip4_frags_ops = { .init = ipv4_frags_init_net, .pre_exit = ipv4_frags_pre_exit_net, .exit = ipv4_frags_exit_net, }; static u32 ip4_key_hashfn(const void *data, u32 len, u32 seed) { return jhash2(data, sizeof(struct frag_v4_compare_key) / sizeof(u32), seed); } static u32 ip4_obj_hashfn(const void *data, u32 len, u32 seed) { const struct inet_frag_queue *fq = data; return jhash2((const u32 *)&fq->key.v4, sizeof(struct frag_v4_compare_key) / sizeof(u32), seed); } static int ip4_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr) { const struct frag_v4_compare_key *key = arg->key; const struct inet_frag_queue *fq = ptr; return !!memcmp(&fq->key, key, sizeof(*key)); } static const struct rhashtable_params ip4_rhash_params = { .head_offset = offsetof(struct inet_frag_queue, node), .key_offset = offsetof(struct inet_frag_queue, key), .key_len = sizeof(struct frag_v4_compare_key), .hashfn = ip4_key_hashfn, .obj_hashfn = ip4_obj_hashfn, .obj_cmpfn = ip4_obj_cmpfn, .automatic_shrinking = true, }; void __init ipfrag_init(void) { ip4_frags.constructor = ip4_frag_init; ip4_frags.destructor = ip4_frag_free; ip4_frags.qsize = sizeof(struct ipq); ip4_frags.frag_expire = ip_expire; ip4_frags.frags_cache_name = ip_frag_cache_name; ip4_frags.rhash_params = ip4_rhash_params; if (inet_frags_init(&ip4_frags)) panic("IP: failed to allocate ip4_frags cache\n"); ip4_frags_ctl_register(); register_pernet_subsys(&ip4_frags_ops); }